GPSD cannot read UDP GPS feed

Question

I have a strange issue with trying to get GPSD up and running on Ubuntu 22

I have the daemon installed and I can use cgps to see status, but gpsd is simply not reading GPS data from my UDP feed.

I can use netcat to verify UDP data is indeed flowing on UDP port 52119:

nc -lu 52119 $GPZDA,164400.64,11,06,2024,,*61 $GPGGA,164400.64,5004.540730,N,14448.387343,W,2,08,1.3,0.32,M,-5.11,M,1.2,0001*46 $GPGLL,5004.540730,N,14448.387343,W,164400.64,A,D*7A $GPVTG,359.27,T,344.21,M,0.3,N,0.5,K,D*2A $GPRMC,164400.64,A,5004.540730,N,14448.387343,W,0.3,359.27,110624,15.1,E,D*2A $GPHDT,219.35,T*09 $PSXN,20,0,0,0,0*3B $PSXN,23,-0.79,-1.46,219.35,-0.38*1F

But running gpsd shows no data incoming:

sudo gpsd -N -D5 -G -F /var/run/gpsd.sock  udp://0.0.0.0:52119

gpsd:PROG: control socket opened at /var/run/gpsd.sock
gpsd:INFO: launching (Version 3.22)
gpsd:IO: opening IPv4 socket
gpsd:IO: opening IPv6 socket
gpsd:INFO: listening on port gpsd
gpsd:PROG: NTP: shmat(33,0,0) succeeded, segment 0
gpsd:PROG: NTP: shmat(34,0,0) succeeded, segment 1
gpsd:PROG: NTP: shmat(35,0,0) succeeded, segment 2
gpsd:PROG: NTP: shmat(36,0,0) succeeded, segment 3
gpsd:PROG: NTP: shmat(37,0,0) succeeded, segment 4
gpsd:PROG: NTP: shmat(38,0,0) succeeded, segment 5
gpsd:PROG: NTP: shmat(39,0,0) succeeded, segment 6
gpsd:PROG: NTP: shmat(40,0,0) succeeded, segment 7
gpsd:PROG: successfully connected to the DBUS system bus
gpsd:PROG: shmget(0x47505344, 24512, 0666) for SHM export succeeded
gpsd:PROG: shmat() for SHM export succeeded, segment 41
gpsd:INFO: stashing device udp://0.0.0.0:52119 at slot 0
gpsd:INFO: running with effective group ID 20
gpsd:INFO: running with effective user ID 133
gpsd:INFO: startup at 2024-06-11T16:47:18.000Z (1718124438)

I have also tried variations on the interface address:

sudo gpsd -N -D5 -G -F /var/run/gpsd.sock udp://10.3.0.255:52119

sudo gpsd -N -D5 -G -F /var/run/gpsd.sock udp://:52119

and cgps shows no data:

┌───────────────────────────────────────────┐┌──────────────────Seen  0/Used  0┐
│ Time:          n/a (0)                    ││GNSS   PRN  Elev   Azim   SNR Use│
│ Latitude:        n/a                      ││                                 │
│ Longitude:       n/a                      ││                                 │
│ Alt (HAE, MSL):        n/a,       n/a     ││                                 │
│ Speed:           n/a                      ││                                 │
│ Track (true, var):                n/a deg ││                                 │
│ Climb:           n/a                      ││                                 │
│ Status:         NO FIX (0 secs)           ││                                 │
│ Long Err  (XDOP, EPX):  n/a ,  n/a        ││                                 │
│ Lat Err   (YDOP, EPY):  n/a ,  n/a        ││                                 │
│ Alt Err   (VDOP, EPV):  n/a ,  n/a        ││                                 │
│ 2D Err    (HDOP, CEP):  n/a ,  n/a        ││                                 │
│ 3D Err    (PDOP, SEP):  n/a ,  n/a        ││                                 │
│ Time Err  (TDOP):       n/a               ││                                 │
│ Geo Err   (GDOP):       n/a               ││                                 │
│ ECEF X, VX:              n/a    n/a       ││                                 │
│ ECEF Y, VY:              n/a    n/a       ││                                 │
│ ECEF Z, VZ:              n/a    n/a       ││                                 │
│ Speed Err (EPS):        n/a               ││                                 │
│ Track Err (EPD):        n/a               ││                                 │
│ Time offset:            n/a               ││                                 │
│ Grid Square:            n/a               ││                                 │
└───────────────────────────────────────────┘└─────────────────────────────────┘

{"class":"VERSION","release":"3.22","rev":"3.22","proto_major":3,"proto_minor":14}
{"class":"DEVICES","devices":\[{"class":"DEVICE","path":"udp://10.3.0.255:52119","activated":"2024-06-11T16:48:19.450Z"}\]}
{"class":"WATCH","enable":true,"json":true,"nmea":false,"raw":0,"scaled":false,"timing":false,"split24":false,"pps":false}

I have also tried running GPSD as a service with the following parameters but no joy

GNU nano 6.2                                                     /etc/default/gpsd  
#Devices gpsd should collect to at boot time.
#They need to be read/writeable, either by user gpsd or the group dialout.\*\*
DEVICES="udp://10.3.0.255:52119"

#Other options you want to pass to gpsd
#Default settings for gpsd.
START_DAEMON="true"
GPSD_OPTIONS=""
USBAUTO="false"
GPSD_SOCKET="/var/run/gpsd.sock"

Any ideas on how to get GPSD up and running with a UDP feed in this manner?